It is well known that, at extrusion temperatures, silane modified hydrolyzable thermoplastic copolymers are prone to scorch or to show incipient crosslinking in the presence of silanol condensation catalysts. Generally, the silane modified copolymer is preblended with a catalyst masterbatch and then the blend is introduced into an extruder at temperatures of 100.degree. to 250.degree. degrees Centigrade. In some situations, the masterbatch is mixed into the resin in the extruder. In any case, within this temperature range, condensation reactions initiate which lead to scorch or premature crosslinking. When scorch occurs, the extrudate begins to show lumps of partially crosslinked polymer. At this point, the extruder must be stopped and cleaned, and the extrudate discarded.